Tap



. c- E. WI MS Patented Jan. 12, 1926.

UNITED STATES PATENT'OFFICE- CHARLES E. WILLIAMS, OF MANSFIELD,MASSACHUSETTS. ASSIGNOR .TO BAY STATE TAP & DIE COMPANY, OF MANSFIELD.

MASSACHUSETTS.

MASSACHUSETTS, A CORPORATION OF TAP.

Application filed May 31, 1924. Serial No. 716,884.

tapping out the hole. With some kinds of metal this producessatisfactory results but with other kinds as, for instance, stringymetal, forgmgs, steel stampings, cast steel,

- etc., the tap so made tears the thread.

I have found by experiment that if one of the walls of each thread islowered far enough to give it clearance so that it will not cut and theother wall does all the cutting the friction is greatly reduced, thetearing of the threads is obviated and a much clearer, smoother threadis formed in the work. 'I have found further that the bestv results areobtained by lowering the walls of the threads on alternately oppositesides so that not only does each thread have only one cutting wall butthe cutting walls of two proximate threads Will come in immediatesuccession followed by two successive non cutting walls, one on each oftwo proximate threads; also that the walls which serve as cutters shallbe so disposed with re lation to each other that the apex of theconverging cutting walls shall be atthe bottom of the thread instead ofat the top. v The advantages of this invention are especially great intaps with tapered threads, but it is not limited to use in such taps.

The invention will be fully understood from the following descriptionwhen taken in connection with the accompanying drawings and the novelfeatures thereof will be pointed out and clearly defined in the clalmsat the close of this specification.

In the drawings:

Fig. 1 is a view in elevation of a tap em? bodymg the invention.

Fig. 2 is a section on line 22, Fig. 1.

Fi 3 is a development showing the staggere relation of the cutting edgesof the threads of one land to the threads of another land. Fig. 4 is aview in profile of the threads of the several lands showing the relationof the cutting edges and the lowered portions, the dotted lines showingthe edges after the wall has been lowered to give the clearance.

Fig. 5 is a sectional view showing the effect of the threads of one ofthe lands of the tap on the work. v

Fig. 6 is a view similar to Fig. 5 showing the effect of the threads ofthe next succeeding land which are in staggered relation to those shownin Fig. 5.

Referring now to the drawings:

There is shown at 1 the shank of a tap with tapered threads having fiveflutes 2 dividing the tap into five lands in which are formed the spiralthreads. For convenience of reference the five lands are designated 25t, t, f, and t also for con-- venience of reference the face or wall ofback face or wall.

The cutting sides are designated a and the non-cutting sides I). Forfurther convenience in distinguishing the non-cutting sides from thecutting sides, the non-cutting sides are lined or shaded in Figs. 1 andIf the threads are formed with uniform distance between their apices andwith the same angle of face as shown by the-full the same thread will bereferred to as the lines in Fig. 4, both walls of each thread will actas cutters when the tool is in operative position. In order to rendercertain of the sides inoperative, that is to be' noncutting, the wallsof said sides are cut back or lowered to give clearance,. as shown bythe dotted lines in Fig. 4., a suitable distance so that they will beentirely free from engagement with the work, as shown in Figs. 5 and 6,while the other sides are operative to do the cutting. Furthermore,instead of having the cutting and non-cutting walls in regularalternation, that is, all of the front walls formed as cutters and allof the rear walls as non-cutters, or vice versa, the

threads are so formed that'the cutting walls or sides of two proximatesuccessive threads Wlll come in immediate succession, and then twonon-cutting .walls; that is, ifthe front face of one threadis'non-cutting, the rear face of that same thread and the front face ofthe next following thread will both be cutters and the rear face of said.second thread and the front face of the third thread will benon-cuttcrs and so on as clearly shown in Fig. 3.

Another feature of the invention consists in staggering the cuttingwalls or sides of the thread of each land with relation to the cuttingwalls of the adjacent lands both preceding and following, as clearlyshown I in one land will be in helical alignment with a pair of adjacentnon-cutting walls of the proximate preceding and following lands.

In order to provide a continuous staggered relation it is necessarythere be an odd number of flutes thereby producing an odd numberoflands. In the form shown in the drawings the tap is shown with fiveflutes and five lands.

As shown in the drawings the groove between the non-cutting sides of thewalls is cut to a greater depth than the groove between the cuttingwalls. This is convenient in reducing the non-cutting wall during theformation of the tap although not essential to the invention.

What I claim is:

1. A tap having the threads so formed and arranged that one wall of eachthread will have cutting engagement with the work, the opposite wall ofeach thread being so relieved that it will not have cutting engagementwith the work, the cutting walls being on alternately opposite faces ofthe successive threads so arranged that there will be two proximatecutting walls followed by two proximate non-cutting Walls and so on inthe same manner.

2. A fluted tap having the threads so formed and arranged that one wallof each thread will have cutting engagement with the work, the oppositewall of each thread being so relieved that it will not have cuttingengagement with the work, the cutting walls being on alternatelyopposite faces of the successive threads so arranged that there will betwo proximate cutting walls f0llowed by two proximate non-cutting wallsand so on in the same manner, each air of proximate cutting walls ofeach lan being in helical alignment with a pair of adjacent non-cuttingwalls of the proximate preceding and following lands.

3. A fluted tap having. the threads so formed and arranged that one wallof each thread will have cutting engagement with the work, the oppositewall of each thread being so relieved that it will not have cuttingengagement with the work, the cutting Walls being on alternatelyopposite faces of the successive threads so arranged that there will betwo proximate cutting walls followed by two proximate non-cutting wallsand so on in the same manner, the cutting and non-cutting walls of eachland being in staggered relation with respect to the cutting andnon-cutting walls of the proximate lands.

4. A tap having the threads so formed and arranged that one wall of eachthread will have cutting engagement with the work, the op osite wall ofeach thread being so relieved that it will not have cutting engagementwith the work, the cutting walls being on alternately opposite faces ofthe successive threads of each land and being so arranged that therewill be two proximate cutting walls followed by two proximatenon-cutting walls and so on in the same manner, the cutting andnon-cutting walls of each land being in staggered relation with respectto the cutting and non-cutting walls of the proximate lands, thenon-cutting walls being so formed relative to the cutting walls as toafford clearance to prevent contact with the work.

In testimony whereof I aflix my signature CHARLES E. WILLIAMS.

